How to connect Firewire 400/800 devices to new iMacs (2017) for VHS transfer

I'm completely frustrated, so any help would be appreciated. On my old iMac (2010), I regularly transferred VHS tapes using a Canopus ADVC-300, which has Firewire 400 outputs. I used a 400-800 cable, and the iMac itself had a Firewire 800 input...so no problem. The new iMac (2017) doesn't have any such input, and while it has Thunderbolt 3 inputs, I can't find any type of adapter that will allow me to hook up my old equipment.

I tried purchasing this cheap USB connector as an alternative, but I'm really unhappy with the sound quality. (https://www.amazon.com/gp/product/B07448TTTH/ref=oh_aui_detailpage_o05_s00?ie=UT F8&psc=1)

So I guess I have two questions:

1 - Is there any way to still connect the old Firewire devices at all, or is all my old equipment now obsolete?

2 - If there is no way to connect it, does anyone have recommendations for a higher-quality VHS transfer device that won't break the bank?

Thanks in advance.