About three quarters of Finland is forest, the highest share in Europe. Cutting down a small area is blown out of proportions, they could of course plant trees to offset in another place. Put every datacenter on Earth together and the land would hold maybe 20 million trees, about 1 in 150,000 of the world’s trees, or half a day of global deforestation.
It is not really forest, but plantation, actively managed and quite low in nature values/diversity. There is a push from EU to conserve the last remaining primary forests in Finland, but it is being opposed by the government and industry.
A big part of that fight is setting up the criteria for primary forests, so I can't easily give you a percentage number of how much of Finland is forest. But not much.
Much of it is planted forests (of native species). Some of those planted forests are for logging purposes and some of it is for GTR purposes to protect biodiversity.
A lot of what Google cut down was planted forests, but the crucial part here is they also cut down some really rare native forests.
That's what they say every time they cut a tree in the Amazon, too.