Translate this plugin in same as all other wordpress plugins. But translation file may be kept in other folder for other plugins.

For this docs we suppose our language code is en_US (for your translation use your own language code).

So translated file name have to be front-end-pm-en_US.po and front-end-pm-en_US.mo (Change language code en_US with your own language code).

You can keep this file in wp-content/languages/plugins OR wp-content/plugins/front-end-pm-pro/languages folder (Both will work).

We can use https://poedit.net/ to create our translation. You can follow following steps to create your own po and mo file using Poedit.
Download Poedit from above link if you do not have already installed.

Create New Translation:

If you do not already have your po & mo file, follow this procedure.

1. Run Poedit
2. File > New from POT/PO file
3. Point front-end-pm-pro/languages/front-end-pm.pot
4. Select your language
5. File > Save As
6. Save file name as front-end-pm-en_US.po (Change en_US with your language code)
7. Catalog > Update From Sources
8. Now translate strings (texts) to your language
9. File > Save (this will update both po & mo file)

Modify Translation:

If you already have your po & mo file, follow this procedure. Keep/copy your po file to front-end-pm-pro/languages folder

1. Run Poedit
2. File > New from POT/PO file
3. Point front-end-pm-pro/languages/front-end-pm-en_US.po (Change en_US with your language code), You may need to change dropdown to show po files.
4. Select your language
5. File > Save (If file name promoted select your previous file)
6. Catalog > Update From Sources
7. Now translate strings (texts) to your language
8. File > Save (this will update both po & mo file)

Using Loco Translate Plugin

1. Dashboard > Loco Translate > Plugins > Front End PM PRO > Edit Template > Sync > Save
2. Dashboard > Loco Translate > Plugins > Front End PM PRO > {YOUR LANGUAGE} > Sync > Save
3. Now translate if there is any untranslated string.