And there is nothing that matches 1000rpm/6cfm and 12vdc. My question is, can I get a fan that has for example 6 CFM and 4000 RPM or does the fan have to be the same RPM as the specs that the vendor states. I am under the impression that the CFM number which is the flow per minute is the important number, and in this case a slow flow is what is important for the project. Please correct me if I am wrong. Thank you.
I agree you want 6 CFM. How you get 6 is not important.
I think lower RPMs will cause less noise.
Probably a high RPM motor will have small blades. A low RPM motor will have many large blades.
Do you have some preferred dimension? You could simply run a larger more powerful fan at lower RPM to get the required flow. However there will likely not be any easy way to realate % of max RPM to airflow, so it it will be more of a guesstimate.
So you have your three important parameters: size, airflow and voltage.
You can go to Digikey's website and perform a filtered search.
You could find a situation where there are no 12 volt, 70X70 mm fans that have exactly 6 CFM. In that case, widen that parameter search, let's say from 6 to 9 CFM.
As others have mentioned, lower RPM usually results in lower noise, which may be important in certain applications.