How do you generate an srt file, please?

Hello,

Would anyone know how I would generate an srt file for my closed captioning, please?  My agency wants to post onto YouTube and needs both the MP4 file and an srt file.  I use Cp 6, btw.  I exported the Word doc that results from selecting Project Captions and Closed Captions.  I'm told they can't work with this.  They need the srt file or equivalent, e.g., smi/sami, svb/sub, rt, etc.

Thank you,

Jeanne