The amount of cooling capacity or tonnage that you need for your commercial space depends on several factors, such as:
The size and layout of your room
The number and type of windows and doors
The insulation level
The occupancy level
The lighting and equipment load
The climate zone
However, a rough estimate is that you need about one ton of ac per 300 to 400 square feet of commercial space.
To get a more accurate calculation, you should consult a professional HVAC contractor like Emergency AC & Plumbing, who can perform a load analysis and recommend the right size of ac for your space.