The 2018 tax return forms include a Form 1040 and six possible schedules--and not everyone has all of the schedules as part of their return. You only get the ones that were required by the data you entered. If your return does not have a schedule 1 or schedule 2 it is because you did not need them. The FAFSA forms ask for the information to be entered IF you had those schedules.
Here is what they look like: Do you think you entered any of the information that would have gone on these?
If the FAFSA questions are telling you to subtract line whatever from another line somewhere--just use "zero" for the "missing" lines--you do not have those lines.