I need to get ready for a 2km run I have only 1 day to prepare and I usally run short distance like 100m dash and 200m
With a day to go, you know you've left it too late to do anything that will make a significant difference. All you can do at this stage is turn up, set off a pace you think you might be able to maintain for 2 km and see what happens. Worst case, you walk.
The only thing I can suggest is to go for a 2 km run right now. If you find you need to walk, set off slower tomorrow. If you manage the whole thing without walking, set off faster tomorrow.