Cascade Thuderbolt (tb) 3 to tb2 daisychain and to USB-C

Have following setup. Macbook Pro (mbp) with two thunderbolt ports. A Drobo thunderbolt 2 disk with daisychain ability (two ports) and now need to connect USB-C portable disk. mbp connects to Drobo via Apple tb3->tb2 connector and tb2 cable. When I plug tb2 cable to Drobo's second port with tb2->tb3 connector to USB-C port nothing happens. All this since need to copy a massive volume, need power supply, but mbp has only two ports.