Backing up your Fonts
Launch FontBook in Applications > FontBook or by searching for it in Spotlight.
Make sure the “All Fonts” is selected in the left window.
Click a font name in the middle window and go to Edit > Select All (or press <Command> - A - ⌘A) to select all fonts. All the font names will be highlighted when they are selected.
Click File > Export Fonts or Export
Name the folder with a descriptive name such as “Fonts Backup+date” and change the save location to your Desktop so you can locate the file easily.
Locate the font backup folder that you just created and click the File menu and pull down to "Compress <your file name>"
Once the file is compressed, you will have a file on your Desktop named <your file name>.zip. In this example it would be Fonts Backup 4-30-18.zip This is the compressed file.
Take the newly created compressed (.zip) file and copy it to your Google Drive and / or external backup media.