Newbie Stuck on Removing White Background

[font="Noto Sans", Arial, sans-serif]I had a student of mine create a logo for our organization to use, and I'm looking to use this logo on various apparel options. When I received a mock-up back, the logo looked too dark against a dark gray hoodie. It was suggested to turn the logo from dark green to white and try it this way.[/font]
[font="Noto Sans", Arial, sans-serif]The student who created the logo has since graduated so she is unable to help further. Using some tutorials I was able to change the logo to white, and it looked like I was able to remove the background as the checkerboard background appears. But, unfortunately when I save the file as a PNG, JPEG, or TIFF I still have the white background. I tested this out by placing the logo in PowerPoint and the white background remains.[/font]
[font="Noto Sans", Arial, sans-serif]If anyone has any suggestions, or has a resource that can help, I appreciate it![/font]

Have you verified that an alpha channel exists for the document?
https://www.youtube.com/watch?v=dMG7GYUCX4U

Also, a JPEG file will not save transparency data, but a PNG or TIFF or TGA should.