Okay First I should teach you numbers I think.
1- unu
2- du
3- tri
4- kvar
5- kvin
6- ses
7- sep
8- ok
9- naĆ (or naux) pronounced 'now'
10- dek
Then to count further you mix them like:
11 would be dek unu (ten one)
21 would be dudek unu (two ten's and one) Get it?