Not too many since I think the flood was local. It was mostly focused on saving domestic animals as evidenced by taking seven of each.
About two million have been described by science. There's estimated to be up to 10 million. Of course that includes a lot of microorganisms.
But on the earth today there are approximately:
300,000 species of flowering plants.
5000 species of mammals
10,000 species of birds
8,000 species of reptiles
30,000 species of fish
950,000 species of insects
Estimated run up to 5 billion species have ever existed.
But when we look at diversity - the current number of species is larger than at any time in the past. But most of the species in the past are not the same species alive today.