bikes have rear cassettes that range from 6 to 12 cogs. there are several different chain widths designed to work with the various cassettes, as well as the front chain rings. according to the Park Tools website, Some nominal widths measured across the rivet between chains are:
12 rear cogs — 5.3 mm
11 rear cogs — 5.5 mm
10 rear cogs — 6 mm
9 rear cogs — 6.5 to 7 mm
6, 7, and 8 rear cogs — 7 mm
When converting to a mid drive e-bike, you get a front chain ring. Is that front chain ring designed to work with any width chain ?