Postwar

To get that plate out you need to spread the frame side plates apart. I've done this on other locomotives using needle nose pliers in reverse (i.e. open the handles to spread apart the frame. Spread just enough so you can rock out the tabs on the bottom plate.

Do you have a picture on where those frame side plates are? I just wanna be careful with this and to make sure I don’t ply apart the wrong thing.

Here is a markup. The red ovals are the tabs on the bottom plate. The green arrows are the side plate you need to spread to give clearance to remove the bottom plate. The bottom plates are brittle and can  crack, chip, and splinter so be careful.

What length of needle nose pliers  did you use, a brand will also be nice.

There really isn't any reason to remove it.  I would clean it intact, bend the spring contacts down with an "L" shaped coat hanger slipped under them and pressed down with a screwdriver before inserting new pickup shoes.  The plate usually breaks if you try to remove it as you really can't spread the frame enough to pop it out, especially with the wheels installed.