Don't freak out. I'm not a doctor, but squamous cells are a normal cell type, different from "squamous cell carcinoma" that you're probably worrying about. I don't know whether or not they should be in an endometrial biopsy (They're definitely found normally in the cervix). But you should talk to your doctor before getting all worried.

You didn't mention why they were doing a biopsy, but my guess from this report is that they will think this sample is inadequate and will want to do a D&C to get a more complete sample.