Hi Connie, a bit of baking soda moistened with water and rubbed onto the rusty area should work well. Another way might be to use vinegar, as the acidity of it will help destroy the rest. Here's a video that will show you how, if the piece is more intricate.
Hope this helps!
Connie: maybe this will help
Here are some more tips: https://www.tipsbulletin.com/how-to-clean-pewter/
Try CLR it removes rust from just about everything. Read the instructions and wear rubber gloves. Good Luck