How do I export a voice memo from computer

Welcome to the Apple Support Communities!

If I understand your question, you have transferred your voice memos from your iPhone to your MacBook Pro and now you want to send them to someone. How did you transfer the voice memos? Did you sync with iTunes? If so, these audio files are stored on your computer in the iTunes Media folder and will have the extension .m4a after the file name.
Syncing the files does not delete them from your iPhone, so if you wanted to send them to someone in an email or a text message, you could still do that using the Share menu on the iPhone.
However, if you did delete the Voice Memos from your iPhone, you could attach the file to an email or upload them to a website. (I'm not sure what you mean by "export" in the title.)
The easiest way to do this is:
1. Open Finder
2. Click on the Music folder in the sidebar.
3. Double-click to open the iTunes folder
4. Double-click to open the iTunes Media folder.
5. Double-click to open the Voice Memos folder
6. Click once to select the voice memo file(s) you want.
7. Drag the file(s) to the Mail icon on your Dock.
This will create a new email message with the file(s) attached.
8. Choose who you want to sent the email to, click in the body of the message to type your message, and then click Send.
Enjoy your day!