My best advice is to go in with an open mind.
Mammograms can be uncomfortable. Some people find them painful. Some people don’t. Each mammogram takes a short time. You can always ask to stop if a mammogram is not for you. And that is ok. It is your choice.
Some people take paracetamol before they go.
Tie your hair back and don’t wear big dangly earrings or necklaces, as you may be asked to remove them.
Also FYI in the uk - mammograms are rarely done by nurses. They are radiographers or mammographers or assistant practitioners with a speciality in mammograms.