Yes one is obliged to give number and kind (and circumstance that changes the sin…like it was your brother you murdered) for mortal sins (venal sins do not have to be confessed…though it is good and recommended to confess at least some…and they do not need to be in number)
Murder 3x. adultery 1x
If after you examine well your conscience…you are not able to give the number…one does what one can…one approximates as close as one can.
If you can say "between 8-10x…then say that…if “around 5x a month for the last 10 years” or “several times …more than 10” …or “I missed Mass on all Sundays and Holy Days for around the last 20 years” then say so…or if one can say “a number of times at least 50 maybe 80” “about once a month for the last 10 years” then say so…or if all one can say is "I do not really know…but it was “many times” or “many many times” …that is fine (or a few times, several times, alot)
Jesus is the Good Shepherd and he loves you…and will give you again “true life”