There is no automatic way you can use as a feap file. You have two choices (at least)
1. write a program to translate the Abaqus input to a feap one
2. edit the file to remove the extra information
a. for each *Node section make it a COOR section
b. you need to add a field after the node number (feap has a generation option that uses the field)
c. for each *Elem section make it an ELEM section
d. you need to edit each element record to add a generation field and a material set number
e. between each COOR & ELEM defining a cell you will add a *node and a *elem that tell how many node increments to add and how many element increments to add. For example after the first set you would add the records
*node = 106
*elem = 38
After the second one you would add together the values , etc.
This is tedious but would work.
There is a third option and that is to add a feature to the program that would do this automatically, but that would require careful programming in the feap modules.