Where do I go to return? And where is it located?

There is signaling that you can follow, it is by the exit, customers pick up and returns

Due to reconstruction, it's on the left side temporarily.

You will have to enquire in ikea only.

Through exit door but also will be easy if you asked IKEA staff will guide you

To the left if you are entering, all the way at the end of the building and if you are coming from the registers it's on the right.

Go in through the exit doors, its on the left side.