I have small painless bumps on the floor of my mouth. what could they be?

Probably: Most probably normal anatomy that you are just becoming aware of. Small chance it may be pathology. How do you find out? Seek examination by a Dentist.

Salivary gland ducts: It sound like you may be describing the sublingual gland duct openings. There should be 2, one on either side of the mid-line and they can look like little bumps. If not that then it would be a good idea to have it looked at by your dentist.