After my ex-wife married someone else and came back to me, how many talaqs do I have left?

If the earlier separation was fewer than three talaq, according to the majority of scholars the husband has only the remaining talaq, not a fresh three.
Example: you divorced her with one talaq, she married someone else, then divorced and came back to you — you have two talaq left. If the earlier separation was a triple talaq, a new marriage after a second husband gives a full three talaq.
This issue has major consequences, so check the record of earlier talaq with the Syariah Court before contracting the marriage again. See rujuk & remarriage.