Roll a 20 sider (+5 dex bonus +3 Base attack bonus) to see if you hit. And roll a d8 to detemine how much damage you did if you did hit.
plus your goblin +2 damage on the damage roll because you know just where to hit those pesky slimy creatures to take them down.

Jolmah will receive a +2 bonus for flanking for the first attack, after that the goblins will realize what's going on and will be on the attack.