Alaikumassalam wa rahmatullah,
Muflih means successful and Hana means enjoyment and peace. Muflih Hana would mean "Hana is successful," "Successful Hana" though it is more correct to say Mufliha Hana since Hana is female, and in Arabic when an adjective is describing something that's feminine, you add an "a" to the end of it. However, Muflih Hana still makes sense and can be used.
As for Muflihana, it could be two things:
1. If by it you mean a fast way of saying Muflih Hana then it is fine, but in Arabic there is no way to join the two words together to create a new word. In Arabic they will stay separate, but if in English writing you write Muflihana to make it easier to write and say, then it's fine.
2. Muflihana, if it is one word, means "the successful person among us" or "the one who gives us success". This is an acceptable Islamic name, though not used by Arabs. It is formed from Muflih (successful) and ana (ours, among us), not from Hana.
Therefore you can use Muflihana as an Islamic baby name, and by it you can either mean a shortening for the two words of Muflih Hana, or the single word Muflihana which means the successful person among us or the one who gives us success.