This is the 95th most frequent Finnish word.
suomeen
"Suomeen" means "to Finland" in English.
Here 'suomeen' indicates motion towards Finland as per Finnish grammar, using the illative case for destinations.
Matkustan suomeen ensi viikolla.
I will travel to Finland next week.
In this sentence, 'suomeen' is also in the illative case, indicating the person being welcomed is arriving to Finland.
Tervetuloa suomeen!
Welcome to Finland!
The word 'suomeen' here again uses the illative case, showing the movement of the person to Finland for residency.