simple sed question
 

I've been searching for a while now, but everything I've found wants to do the exact opposite of what I need.

I'm looking to replace all newlines in a file with the actual "\n" string.

So, for example. If my file contained:
I would like the output after i type the command to be
Most of the help I've found is to do the exact opposite. I've tried tr and sed, but I'm not abundantly familiar with regex does anyone have a suggestion?

The following should work

UGH! you sir are a saint. Thanks a million!