How to save a hex file into Arduino Flash to send it via Serial?
If I understand your question correctly, you need to integrate this data into a .ino script.  Probably as a byte array. Then the script can read the array and Serial.write its content.

You could write a small tool in Python or else on your computer, that takes the text file and converts it into a .h header. Include that into your .ino script. Or use your favorite text editor to format the data into C++ code, and copy/paste that into your script.