I'm really bad at interpreting intent through typos and grammer troubles (don't worry, I'm not going to harp on you. Everyone makes mistakes, and I know I can't assume that English is everybody's first language and major degree in college). I'm going to re-type your post for my own benefit, and you can tell me if I've completely missed the idea behind what you were asking.
"Hey guys i just need a lil help. Last night in the World's Largest Zoo we finished a hair-raising but poorly thought out CR 23 fight. Being 13th level and the only character that survived, I sort of need a bit of help... Oh and no, this isn't anything good like how to get a new party or anything silly like that. No, the problem I have is being off the bloody Exp chart! In fact, we all were. Does anyone know were I can find rules for working out Exp for when you're off the sodding chart?"
In which case I think this is your answer:
+1 Character level = +1,000 Exp x current character level.
For working out multiple level increases at a time, you'd need a formula using math that I can't remember from high school, so here's a chart:
20th = 190,000 Exp
21th = 210,000 Exp
22th = 231,000 Exp
23th = 253,000 Exp
24th = 276,000 Exp
25th = 300,000 Exp
26th = 325,000 Exp
27th = 351,000 Exp
28th = 378,000 Exp
29th = 406,000 Exp
30th = 435,000 Exp