There are several ways to do this. If your file has some known structure, you can use
grep command searches a file for a specific phrase and returns lines that match that phrase. So if your file looks like
Date of Birth: 7.31.76
Address: 1234 Main St.
you can run
grep Name info.txt and it will return
Name: Sally. You can then redirect the output to another file. So calling
grep Name info.txt > info2.txt
will output the line to the new file info2.txt. If you want to append new lines, you can do
grep Address info.txt >> info2.txt
otherwise the file will be overwritten.
You could also learn to use a command line text editor like vim.