If I have about 30 milliliters of adipose tissue, how would I isolate preadipocytes from it? Also about how many cells would 30mls contain? (estimation)
The amount of adipose derived stem cells (ADSCs) that you can isolate from subcutaneous adipose tissue depends on several factors such as: the donor's age and physiological condition, the tissue harvest site (abdominal, hip, breast, etc), the method you are going to use, etc.
Regarding the isolation, the protocol described by Gimble et al. (Gimble, J.M.; Katz, A.J.; Bunnell, B.A. Adipose-derived stem cells for regenerative medicine. Circ. Res. 2007, 100, 1249–1260.) worked very well for us, as you can see in our paper: Modulation of Adipogenic Conditions for Prospective Use of hADSCs in Adipose Tissue Engineering.
In addition, you can try to purify your primary cell culture using magnetic beads or a cell sorter (flow cytometry).
Hope my answer could be helpful and I wish you good luck with your work.