There's two dead-simple theories on how to convert introvert types from Socionics to MBTT and vice versa:
Now, I find this interesting:
Socionics defines functional extroversion as dealing with bodies (e) versus fields (i).
MBTT defines functional extroversion as whether it seeks stimulation (e) or concentration (i).
Socionics defines functional order as whether something is accepting (1) or producing (2).
MBTT defines functional order as whether something is dominant (1) or auxiliary (2).
For conversion A to hold true, it would imply that 1/e and 2/i are transposed.
For conversion B to hold true, the definitions of the phenomena must be consistent.
Other cases would indicate a more complex conversion process. For example they might need to take subtype into account, or some functional traits might match a certain way where certain others do not. In the case of introvert sensors however, it seems there is a fairly strong match to A, such that Se2 and Si1 are transposed, along with the function they are paired with.