Combining Access databases logically

I have two separate databases, Db A has data from 1944-79, and Db B has data from 1944-98. They both have an ID, year, and Tritium columm, but there is other information in columns that aren’t necessarily the same for both databases. Unfortunately, the Tritium values in Db A are incorrect, and need to be replaced with those in Db B. Also, Db B has many more entries than Db A.

What I need to do is search Db B for lines where the ID and year match those in Db A, then replace the Tritium data in Db A with that from Db B, which has the new, correct tritium dose data.