While some models of portable camping grill come with hookups for full size propane tanks (the Blackstone Tailgater Combo, for instance) most are designed to be lightweight and portable. For this reason they have been designed to operate using 1# disposable propane tanks which are available at most outdoor supply stores and even many gas stations and grocery stores. These tanks are lightweight and small, making for the perfect fuel source for camping trips where space might be limited.
It is usually possible however to fit your portable camping grill with a high-pressure gas line that is specifically designed to handle the specifications of a full-size propane tank. These gas lines are available at most hardware stores, but might require additional pieces of hardware to fit perfectly. Many manufactures actually provide these types of hookups via their online store, so check the specifications on your grill before you buy.
Because of the difference in pressure between 1# tanks and full-size tanks, your portable camping grill might not work the same way with one size tank as it does with another. For this reason it might be necessary to research models that are suited to the tank size of your preference.