Hello Jaymie Cook,
Here is a link for you, which www.acefitness.org suggests:
You may also like youtube videos.
Natalie aka NAPS 2 B Fit.
I like this Facebook group, Somatic Anatomy, for anatomy. It’s not really an anatomy primer; rather, it’s more about how suites of muscles work together.
Last but not least, this is a particularly good book, and it has a companion workbook. I like it better than some of my anatomy books because it gives examples of “real life” movements that you can explain to clients. For example, plantar flexion is like pushing your foot down on a gas pedal.
Trail Guide to the Body: How to Locate Muscles, Bones and More