Error mounting filesystem when mounting external hdd

Hard drives can fail. That is why you have copies of important files and memories on at least two drives, but preferably more. Then, when a drive fails, you do not loose your data.

You used the drive for 10 years. That is a long time for a hard drive to remain operational. Windows 10 does not anymore recognize it. That, now, also Ubuntu does not recognize it confirms you might be dealing with a drive that is end of life. You already tried different computers and now a different operating system. Make sure you also try a different connection cables - it still could be just that.

If all fails, and you do not have any backup of that data, then date recovery will be your only option to try to recover at least something. Using professional services will likely be most successful, but that tends to be very expensive.