how to use thread pool library?

I use newer versions of C++17.

There is a big text file that has a lot of lines (you can think of 10s of millions). I need to develop multi-threaded application that reads lines from input file, reverts character in a single line and writes to output file. Size of the line is unknown.

I'm new in multi-threading that use pool library dynamically in c ++.I need your help urgently.

I tried some code but I got unexpected runtime-error.I hope you will give me a full code for my project.