Drum/Tumbler Won't Turn when Dryer's Running

The Dryer’s Drum/Tumbler will turn by hand but will not turn automatically when the dryer is running. I’m assuming the problem is w/the belt (or pulley). How does one go about repairing/correcting the problem? Would like to avoid the expense of a repair technician when I might be able to resolve the issue on my own.

For the FDE216RBS1 Frigidaire model, which dryer panel (i.e., front, top or back) do I remove to locate the belt/pulley? In addition, is there a specific replacement belt/pulleypart required for the fix?

Thx.