You may need to use a [https://www.amazon.com/Velleman-PCMP12-Y-Cable-Firewire-Connector/dp/B001IXUOD6/ref=sr_1_2?ie=UTF8&qid=1546535127&sr=8-2&keywords=iPod+dock+connector+to+usb+%26+firewire|Y-Cable] and a [https://www.amazon.com/Apple-FireWire-Adapter-Discontinued-Manufacturer/dp/B0000D8LSW/ref=sr_1_5?ie=UTF8&qid=1546535127&sr=8-5&keywords=iPod+dock+connector+to+usb+%26+firewire|FireWire Power Adapter]. This way, you can charge your iPod using FireWire and connect it to your computer via USB at the same time.
It is difficult to find an official Apple Y-Cable, which is why I linked an off-brand version.