See UNO schematics here on web. Original part is LP2985-33DBVR. The LD3985M33R 4A2D is probably some similar chinese part, but it doesn't matter. Any 3.3V LDO in SOT-23 should be fine. See this http://www.ti.com/lit/ds/symlink/lp2985.pdf. Similar according the parameters - LDO 3.3V, 150mA, SOT23.
Do not forget that there can be another problem, not only burned regulator. It can be just cause or result of another faulty part.