What kind of wood have you found?
A lot of woodwork was never intended for anything except paint.
Poplar is a good example. It was always intended to be painted.
Red Gum, Oak and a number of other woods were intended for a stain/clear finish.
Reversing from paint to stain always involves removal of some wood. Any method that removes paint in pores of wood will damage he surface.
If you want to stain the trim look for new trim in stain grade and replace the old material.
Just about nay trim is available for enough $$.
If you are near a big city there should be at least one company that still has all the old patterns.

I dont know types of wood. How would I found out his information. I think I heard it was pine.

Pine is light colored and has lots of close grain lines---at least the pine from that period did.

There was a lot of mahogany used for painted trim back then also, at that time mahogany was considered a secondary wood. Mahocany is darker, less distinctive grain patterns, and denser than pine.

In my first house, every room but one had painted woodwork. I removed and stripped every piece and took it all back to natural. At the time, stripper was cheaper than new molding. In your house, the woodwork is probably REALLY valuable if it is all the old style.

I used Zip Strip. It works well, and very fast. Once you get all the heavy paint off, dip some coarse steel wool into the stripper and scrub off the remaining paint. You'll probably have to use tools like old tooth brushes and picks, or a dull knife to get all the paint out of any beadwork. Afterward, you'll need to sand the pieces because your stain will look patchy if you don't. Just a light sanding with 300 sandpaper. This is very time consuming but the results are worth it. I worked on it in the evenings while watching TV and just did it one room at a time.