Muffler hanger bolts - type?

I've a '92 XJ I-6 Autotranny. Back on the passenger side the tailpipe extends from the muffler up and over the rear axle. In this region there is a rubber shock connected from to the body from a rod welded to the tailpipe. It is held to the body by two bolts.

My bolts fell out !!

Does anyone know how these twp bolts are described so I can walk into the auto parts store and grab them from the proper bin? Otherwise I'll just have to try various possibilities until I find the proper one.

Thanks!