Calculating effect size for a within group comparison of score before&after treatment

Hi all, :wave:

I am wondering which formula will be more suitable for calculating effect size (Cohen's d) of an intervention with scores obtained before (1 score) & after treatment (1 score) in the same group of individuals. :confused: As I had two scores, I used paired t-test for for within group comparison. I would appreciate if somebody could help me with this. :)

Many thanks in advance,