Does this wall charger come with a USB cable, or do I need to purchase it separately?

Yes, the wall charger comes with a USB cable power supply.

Questions & Answers: UpBright Wall Charger + USB Cable Power Supply for Seagate Wireless Plus STCK1000101 STCK1000200 STCK1000300 HDD Seagate Wireless Plus STCK1000100 1TB 1FPBA1-570 Wireless Plus USB 3.0 Mobile Storage

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UpBright Wall Charger + USB Cable Power Supply for Seagate Wireless Plus STCK1000101 STCK1000200 STCK1000300 HDD Seagate Wireless Plus STCK1000100 1TB 1FPBA1-570 Wireless Plus USB 3.0 Mobile Storage

World Wide Input Voltage 100-240VAC 50/60Hz.
OVP, OCP, SCP Protection (OVP: Over Voltage output Protection. OCP: Over Current output Protection. SCP: Short Circuit output Protection).
Tested Units. In Great Working Condition.
UpBright 30 days money back guarantee. 1 full year service warranty.

$50^.99 –