I had protected sex dec.3 had normal period dec. 9 condom broke dec.23 & took planb couple hrs later. What is possible conceive date.?

Conception. 30 min to 7 days (even longer). Assuming all is healthy, sperm may reach fallopian tube in 30 min. However, conception depends on when you ovulate (you don't know that, you can gess). Sperm may survive in fallopian tube for 7 days , even longer. We estimate date of birth based on your last period. Gyn will also do us to estimate age of fetus and date of delivery by making measurements.