All HDV camcorders can play SD tapes
For 8mm you would need
a Hi 8 ,
Digital 8 ( which is backwards capable, not all are)
or
an
old video 8 machine:
as such there is a range of camcorders which widen your choice
For analogue the easiest thing would be to just record to a setop DVD recorder
If you dont have one to access to one you may need to use a pro service, depending on how many tapes you have.
If they are quite a few, you may be better off buying a camcorder and selling it off later
A set top DVD recorder need not be sold off as it will always come in handy