It is not actually possible to "convert" UPF image files to MMS format. However, you can send a MMS with the photo saved as .upf file using your Nokia phone.
This was probably something that users required few years back when this type of files was used in older Nokia devices. Otherwise, we do not know about any other upf to mms conversion.
Unfortunately, there is no detailed software record in the database that match this conversion.
UPF
A upf file extension is related to the some Nokia mobile phones. A upf file stores digital photo.
MMS
Files with mms extension can be most often found as multimedia messages saved in special Multimedia Messaging Service message file format. An .mms file stores multimedia objects (images, audio, video, rich text) sent through mobile phones with MMS support.