You can convert UA miles to Marriott points.

https://marriottbonvoy.unitedmileageplus.com/

Edit:

Transfer MileagePlus miles into Marriott Bonvoy points
Convert up to 100,000 miles into Marriott Bonvoy points each calendar year at a 1-to-1 ratio. This benefit is only available for MileagePlus Premier members.

It doesn't look like you have UA status, but I will leave this post here in case it helps someone else.

Here are other transfer options.

https://www.marriott.com/loyalty/ear...s-to-points.mi