A unit to feed blanks in a packer machine and comprising: a frame ; a hopper , which is supported by the frame , is designed to hold a stack of blanks and has a pick-up opening , through which one blank at a time can be picked up from the stack of blanks ; and a conveyor , which is supported by the frame and moves the blanks along a moving path (P), which ends in the hopper ; wherein the frame comprises a support body , which is provided with a seat designed to house the hopper ; and wherein, in order to contain blanks with different formats, the feeding unit can be adjusted by means of a format change operation, which entails changing the feeding unit from a first configuration, which is suited to contain a first format of the blanks , to a second configuration, which is suited to contain a second format of the blanks , which is different from the first format; the feeding unit is characterized in that: a plurality of different and interchangeable hoppers is provided, each associated with a corresponding format of the blanks ; each hopper is fixed to the frame in a removable manner in order to be replaced during a format change operation so that the format change operation entails replacing a first hopper associated with the first format with a second hopper associated with the second format; and the support body is movable on the frame so as to move, during a format change operation, between a work position, in which the hopper housed in the support body is coupled to and aligned with the conveyor , and a replacement position, in which the hopper housed in the support body is uncoupled from and not aligned with the conveyor . a frame ; a hopper , which is supported by the frame , is designed to hold a stack of blanks and has a pick-up opening , through which one blank at a time can be picked up from the stack of blanks ; and a conveyor , which is supported by the frame and moves the blanks along a moving path (P), which ends in the hopper ; wherein the frame comprises a support body , which is provided with a seat designed to house the hopper ; and wherein, in order to contain blanks with different formats, the feeding unit can be adjusted by means of a format change operation, which entails changing the feeding unit from a first configuration, which is suited to contain a first format of the blanks , to a second configuration, which is suited to contain a second format of the blanks , which is different from the first format; the feeding unit is characterized in that: a plurality of different and interchangeable hoppers is provided, each associated with a corresponding format of the blanks ; each hopper is fixed to the frame in a removable manner in order to be replaced during a format change operation so that the format change operation entails replacing a first hopper associated with the first format with a second hopper associated with the second format; and the support body is movable on the frame so as to move, during a format change operation, between a work position, in which the hopper housed in the support body is coupled to and aligned with the conveyor , and a replacement position, in which the hopper housed in the support body is uncoupled from and not aligned with the conveyor . a plurality of different and interchangeable hoppers is provided, each associated with a corresponding format of the blanks ; each hopper is fixed to the frame in a removable manner in order to be replaced during a format change operation so that the format change operation entails replacing a first hopper associated with the first format with a second hopper associated with the second format; and the support body is movable on the frame so as to move, during a format change operation, between a work position, in which the hopper housed in the support body is coupled to and aligned with the conveyor , and a replacement position, in which the hopper housed in the support body is uncoupled from and not aligned with the conveyor . <EOS>