have a firewire 800 from my camcorder and need to connect to usbc port on new Mac mini

You need two adapters and a cable for a FireWire camcorder:

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

Apple Thunderbolt to FireWire Adapter

FireWire 800 9-pin to 400 4-pin cable

https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter?fnode=d6f1662b62130679cc9a9db672fb246e714dc2ed0e27ef533a0da1c645ed7ae86d3f14b97c21419b47a0e67dee7e3c14be4b65da1c1f0f5724f3c9c7f9350254caa9a698ecf2b50e3e22f209c396a62216a4954927b2a0aa3db4984dbd3c5873f02756ef07b16185b1f1bd974b01eb1f

https://www.apple.com/shop/product/MD464LL/A/apple-thunderbolt-to-firewire-adapter?fnode=144b61092cd38fd0d9c64a3312fc431d93aec7a38cabd963429752dce49d82db2a168084336e19922e2c0c5282c9918bcda03d710a2f525149378e12b570153cea205800e0bdb8d5c76b1805b02cf8917424e7ba432e5dae1af94c1a77b57a28a488aa5bbfdddda40907beb52281a357

https://www.amazon.com/Tripp-Lite-FireWire-Hi-speed-F019-006/dp/B000AAZQM2/ref=sr_1_4?crid=38P09A5IJSGE1&dchild=1&keywords=firewire+800+to+400+4+pin&qid=1596714370&sprefix=firewire+800+to+400%2Caps%2C265&sr=8-4

p.s. I briefly tried my old D8 (essentially the same as miniDV except it uses Hi8 tapes instead miniDV tapes) Sony TRV320E (unnEUtered to allow analog-in and analog-to-DV passthrough so I could use it to digitize all old VHS footage as well) and it worked quite OK in Mojave although occasionally I had to reconnect the cable to make it work. I have an old Mac mini 2009 and also PowerBook G4 2004 for officially supported DV work but I have essentially retired the DV gear by now.

iLife 06 installer doesn't run on OS X 10.7 or later because it is a PowerPC application. iMovie HD 6.0 can be installed via Pacifist ($20): Open the iLife 06.mpkg installer with Pacifist, select the whole iMovie package and let Pacifist install all components to their correct places. iMovie HD 6.0.2 Combo Update and iMovie HD 6.0.3 Update can the be installed normally. iDVD 6.0.4 doesn't run on OS X 10.8. OS X 10.9 is the last where iMovie HD 6.0.3 officially runs, or in macOS 10.10-10.14: Right click to show package contents. Open contents. Open info.plist in Text Editor. Scroll down close to the bottom and locate line:

<key>CFBundleVersion</key>

<string>6.0.3<string>

Change the 6.0.3 to 6.0.5.

I switched to FCP after iMovie HD 6.0.3 and have no experience from later versions or how FireWire works in Catalina or Big Sur (AFAIK it is no longer possible to boot via FW?).