I actually have found the answer, with difficulty, by collating suggestions from lots of people who have had the same problem.
Firstly, as a few people have said, Tasks is now called 'reminders'. If you have reminders, you can click on the little arrow at the end and change it to 'Tasks'
If like me however, you have previously deleted 'tasks' you can get it back really easily. Change the language to English US (Or English UK if you are already in US) and then 'reminders will appear on your list for some reason!
Once it turns up you can change back to the original language you were in!
Very strange, but it worked :-)