How do you get the concentration with buret readings? What would the concentration of HC2H3O2 (M) be?

For example,

Molarity of the NaOH solution: 0.2619 M
Final buret reading: 31.10 ml
Initial buret reading: 0
Volume of NaOH solution: 31.0 ml

concentration of HC2H3O2 (M): ??????

thanks

Final buret reading = 31.10

Initial reading = 0
Volume NaOH = 31.10-0.0 = 31.10 mL.

M NaOH = 0.2619M
mols NaOH used = M x L = ?
mols HC2H3O2 used = the same since this is a 1:1 reaction; i.e.,
NaOH + HC2H3O2 ==> NaC2H3O2 + H2O
M HC2H3O2 = mols HC2H3O2/L HC2H3O2. You know L and you know mols, solve for M.