You need to dump the ROMs from your original Midway Pac Man game cabinet, anything else would be unlawful.
Please don't advertise unlawful actions on these forums.
[St.]
EDIT FOR CLARIFICATION:
So I went to some rom sites downloaded some roms...
The legality of this is very much up in the air, even if you do happen to own an original copy.
It depends very much on your locality in the world, and how far those laws have been pushed/tested.
As such, it is better to avoid the topic altogether.