I always run with my phone tracking me as I like the stats. I have a Xaomi MiBand watch that just counts steps. Something like that may be enough if you just want a rough estimate of what you did.

If you want to go further you could try doing it at a slower pace so your body gets used to going for longer. Speed can come later. I just gradually worked my way up and now I can do an hour plus with no issues. Mind you I'll be doing my longest run on Sunday with a half marathon.