Where can I purchase additional hard drive cadge to install more drive inside the case?

I'm not sure what you are looking for. I installed 6 ssd drives in mine, simply because I had them. The case will take 4x3.5 inch HDDs without any special (extra) mounts. 2 HDDs mount from the back side, and 2 mount from the glass side, but none are accessible without removing the side panels. Only the 5.5 inch is accessible from the front, and is great for your optical drive.

Can this support regular fan cooling?

yes, and lots of them. Down side is only 2 on top if you plan on keeping the optical drive.

Questions & Answers: Rosewill MIRAGE P700 ATX Mid Tower Gaming PC Computer Case, Supports E-ATX, 360mm Liquid Cooler and Long GPU, Optimized Airflow with Side Vents, Expansion Ready, Tempered Glass Panels

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Rosewill MIRAGE P700 ATX Mid Tower Gaming PC Computer Case, Supports E-ATX, 360mm Liquid Cooler and Long GPU, Optimized Airflow with Side Vents, Expansion Ready, Tempered Glass Panels

Superior with Simplicity: Designed with clear tempered glass panels on the front and side, this refined chassis exhibits supreme aesthetics and boasts superb performance with phenomenal potentials. Pre-installed with one 120mm fan in the rear.
Massive Expansion Capacity: Supports E-ATX 12 x 13in large form factor motherboards with builder-friendly layout, spacious interior and full tower potential, capable of housing one 5.25" ODD and up to 6 HDDs/SSDs. Features 8 expansion slots for adding on powerful components to make your system an ultimate dream come true.
Expandable Cooling Potential: Install up to 7 case fans to maximize air intake and ventilation with optional 360mm liquid cooling radiators on front and top, 140mm radiator at rear for delivering robust thermal and operating performance.
Vertical GPU Support: Built with GPU riser bracket for supporting GPU card when vertically mounted.

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