This is not necessarily retention. It could theoretically also be a kidney profusion issue, or any number of other renal problems.
If you have had literally no urine output for a few days then you should see a doctor ASAP.
To give you an idea of what you should be producing if you’re well in yourself and properly hydrated you can use the following formula: 0.5 ml per kg of your weight per hour. ( Obviously this doesn’t have to come out religiously once an hour every hour but over all that’s the kind of amount you should make.)
E.g if you weigh 60kg and haven’t urinated for 3 hours the next time you do you should expect around 90ml. Don’t get too carried away with micro managing this, urine output will vary through the day, it’a long term under production that is potentially problematic.