The file you are looking for
It is called transactions.csv, and its header row reads Date, Description, Original Description, Amount, Transaction Type, Category, Account Name, Labels, Notes. If you exported anything from Mint before it closed, this is almost certainly what you have.
Amounts in a Mint export are always positive; the Transaction Type column carries the sign. Footnote reads that column, so a file that looks like it has no spending in it will still import correctly.
Import it
Open Footnote, go to the account screen, choose Mint as the source, and upload the CSV. Dates in either M/D/YYYY or YYYY-MM-DD are read, which covers both the export and the versions people have re-saved through a spreadsheet since.
Rows are matched to your connected accounts by the Account Name column. Anything that does not match becomes its own account rather than being dropped.
Why it is worth doing
A bank connection typically serves two years of history, and often less. A Mint export goes back as far as you used it. That difference is what makes multi-year questions answerable at all: what a subscription cost before three price rises, whether a bill is actually seasonal, which duplicate account you forgot about.
There is more on what changes in coming from Mint.