In theory, yes - but it may not be a simple "point and click" solution. Atlassian provide an open sourced tool for migration, but they don't support it:
and here are the notes about MediaWiki specifically https://migrations.atlassian.net/wiki/display/UWC/UWC+Mediawiki+Notes
I'm assuming if you can export MediaWiki into the right format for Confluence Cloud, you can then import.
Do you use templates with Confluence? Take part in a remote 1-hr workshop. You'll receive USD $100 for your time! We're looking for people to participate in a remote 1-hr workshop...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs