You would need UF-B direct burial cable. Which you can also run in non-metallic conduit for extra protection. It should be 18”+ deep if in conduit, 24” otherwise. You’ll also need to keep the wire in conduit from below grade into the building. By the way, 12/2 is rated 20A max and its a violation to use a breaker greater than that. This isn’t too complex, just a branch circuit to a detached building.

I am doing something similar with a shed, but need a bit more power and wanted to run only a single cable. And I do not need the extra capacity or complexity of a sub-panel. So I am using a ‘Multi-Wire Branch Circuit’ which is 12/3 plus ground. This will split a 240V connection into two 120V circuits. The only downside is that this requires a 240V breaker (or two tied 120v breakers) and both circuits must be powered down together. There are also some details concerning GFCI protection. Not a deal breaker for me.

Disclaimer: I am not an electrician, etc.