If I get the USB-C to Thunderbolt 2 adapter, what wire am I connecting to the adapter on the second pic?

I've never owned that camera but are you looking for this? You'll need a thunderbolt 2 on your machine to plug it into https://www.amazon.com/dp/B00WVDGZM6/ref=cm_sw_r_cp_apa_i_PVJuFbZV5G5M1

Or an adapter like this? https://www.amazon.com/dp/B01MQ26QIY/ref=cm_sw_r_cp_apa_i_VWJuFb2D152TJ

4/5 stars on Amazon with the top description mentioning Sierra and the third reviewer mentioning using it for their 2013 MBP with Thunderbolt 2 ports.

Perhaps yours was defective?

You need the following: - Lightning to USB-C cable - OSX Yosemite or earlier (newer versions killed off Target Display Mode) - Intel Based iMac, which I’m sure you have being 2012.

I use this one: Apple Thunderbolt 3 (USB-C) to... https://www.amazon.com/dp/B01MQ26QIY?ref=ppx_pop_mob_ap_share

There is an old matrix online that I used to make mine work, I’ll have to look for it to share when I find it.

I think you're best off getting a TB3 drive and use the Apple TB2 - TB3 adapter https://smile.amazon.com/dp/B01MQ26QIY/

You likely won't find a tb2 drive that you want.

Are you sure the drive is USB-C and not Thunderbolt 3? Because that'll determine the appropriate adapter.

Also, if it's Thunderbolt 3, is the cable built-in or is there a port on the drive into which you plug the cable?

For USB-C this should work: https://www.amazon.com/Satechi-Type-Type-C-Adapter-Converter/dp/B07KCL8WZK/

And for Thunderbolt, this is what you need, note it requires the drive to have a port, not a hard wired cable: https://www.amazon.com/Apple-Thunderbolt-USB-C-Adapter/dp/B01MQ26QIY