When shall we (1)/ arrive (2)/ to our destination ? (3)/ No error. (4)

Answer

3

Explanation

at will replace to because
We usually say that someone arrives at a place/arrives in a country/city
Look at the examples given below:
We arrived at the station at 3 o.clock.
The President arrived in Rome today. Use of arrive to is incorrect.
Hence, at our destination is the right usage.