I know I need 4/o alu for 200 amp but do I use ser or sur?

There is no SUR, it's SEU, and it depends on what the service is for.

SUR?? If entrance use SEU, If going from a main panel to a sub panel use SER. SEU does not have a ground wire, 2 hots and a bare neutral. SER has 2 hots, a shielded neutral and a ground