What kind of files do you have? DICOM? NIfTI?

If DICOM, you'll have a file named something like 0001.dcm.nfo for each run of each subject, and within that file, a line like:
which is a 2000 ms repetition time (2 seconds).

If they are NIfTI files, you'll have files named like:
and within those files, you'll find:





If someone handed you this project, you'll probably want to ask them where the documentation for the data is. Someone designed the study and specified the repetition time and the other parameters.