The best airport to go to will be Schiphol (Amsterdam) Airport.
Schiphol has good connections, for example by train.
There is a direct train connection from Schiphol Airport to ASSEN (1hr 54 mins). Take the train in the direction Groningen. This train takes 2 hours and leaves generally 3 minutes past the whole hour and departs from platform 1 or 2.
Get off at the station ‘Assen’.
If needed, you can take bus line 21(Emmen) to Grolloo (20 mins) from there.
You will need an ‘eenmalige chipkaart’ (single use chipcard), obtainable either at the NS-desk at Schiphol Airport or a NS -ticket machine (yellow with blue top). You’ll need a one-way ticket to Assen (25,50 Euro).
From most directions: Highway to Assen (A28/E232) to N33.
From the N33 take the nearest highway exit to Grolloo on the N33 (Exit Rolde). From there 6 km to your destination.