I don’t know what the Hebrew words are in Genesis, but however the process (or time period) He did it, God creating the Universe out of nothing, and He being distinct from that creation, is an essential to a Christian world view—just as essential as God being a trinity. (Also, if love is an essential part of God, then there has to be a plurality in God..that plurality being the trinity—along with an essential unity, God being one.)
Ex nihlo creation (not necessarily what we understand as “creationism”) is a philosophical essential. Evolution (as distinct from naturalist evolutionism...a philosophy) and ex nihlo creation don’t seem to have any necessary essential conflict, in my opinion.
Ex nihilo creation does not appear unambiguously in Gen. That is usually not argued.