1. From the commandline, add the -datadir argument. In your case: -datadir=N:\Bitcoin
or
2. Edit the "shortcut" used to start BitcoinQT so that it includes the -datadir argument:
NOTE: again, for YOUR setup (based on your screenshot) it should be -datadir=N:\Bitcoin
or
3. edit the bitcoin.conf located where the "blocks" folder WAS (likely to be something like: C:\Users\YOURUSER\AppData\Roaming\Bitcoin on Windows), and add a line that says:
Refer here for detailed explanations of how one can move the Bitcoin Core "data directory": https://bitzuma.com/posts/moving-the-bitcoin-core-data-directory/