How to transfer my service to a new unlocked phone

I have been using an unlocked Sony Xperia XA2 Ultra phone, but the screen is cracked.  I happen to own an unused unlocked Google Pixel 3A, still in the box.  How can I transfer my T-Mobile phone service from the Sony Xperia XA2 Ultra phone to the Google Pixel 3A phone?  To complicate matters slightly, I am a mariner aboard a ship that never sees American shores, but rather spends time in European ports.   No problem getting T-Mobile service over here, of course.   Is the solution as simple as moving the SIM from my Sony Xperia XA2 Ultra with the cracked screen to the Google Pixel 3A?  Or are there additional steps that I must take, such as involving T-Mobile customer support?  Naive questions, to be sure.  I’m more of a PC person than a phone person. Thank you so much for some guidance, please.