There is no tax credit for an HSA contribution. Instead, there is an "Adjustment to income" (a deduction not subject to itemizing). It is the full amount of your contribution. So, on line 25 of your 2018 Schedule 1, you should see the ~$3500 you contributed. That may have resulted in an approximate $1000 tax savings, depending on your overall tax situation. But, it was not a tax credit.
For 2019, the HSA deduction shows on line 12 of Schedule 1 (there was a major form redesign for 2019).
