Photos won't play 3gp format

Does anyone have a solution to the fact that unlike iPhoto and Aperture, Photos does not appear able to play 3pg file format. I have a lot of 3gp videos from an old mobile phone that I would like to play in Photos. It refuses to do so although it gives the option of opening in Quicktime which can play them. However, when I try to save the converted format from Quicktime, I am told "Operation cannot be completed."

Apple, please sort this out in Photos and/or Quicktime, otherwise it would appear that Photos is rendering valuable family memories obsolete.