where do I find target market statistics for free, mostly general information.

Depends on region, industry, demographics, etc. Many possible answers without clear target there

I'm looking to make software, its usually across the globe. Primarily Enterprise customers, would like to have like a SAAS model something like this

You need to choose between bottom up or top bottom analysis - seriously, this depends on so many factors - first milestone is being very accurate TAM SAM SOM, otherwise you'll just write features no one needs.

Its not a unique market, I have seen already such platforms, but they are not upto mark

My advice abides even more when the it's not a unique market, meaning there's competition that needs to be taken into account. Better data upfront leads to better decisions later on. IMHO