iMac transfer from my iMac 2009 to new iMac 2020 - adapter cables needed?

Fishrrman's "you can do it!" routine for migrating to a new Mac:

If you follow my instructions below, I guarantee a success rate of 98%:
PRINT OUT these instructions and check them off as you go along.

1. BEFORE you do anything else, run a "final" backup on your old Mac. Use an external drive for this. It can be either TM or a cloned backup using CarbonCopyCloner or SuperDuper. I prefer CCC.
I STRONGLY RECOMMEND THAT YOU DO NOT USE TM AS YOUR "MIGRATION EXTERNAL DRIVE". INSTEAD, USE EITHER CCC OR SD. Things will go better this way!
2. Shut down the old Mac and disconnect the external drive
3. Take the new Mac out of the box and set it up on the table. DO NOT PRESS THE POWER ON BUTTON until step 8 (read on). You don't want to begin setup until "the right moment".
4. If you're using an external display, connect the display using the usb-c/VGA adapter/cable that you have
5. Connect the keyboard and mouse if you use them. I STRONGLY SUGGEST that you connect them DIRECTLY to the Mac.
6. If you use a hub, leave it DISCONNECTED for now
7. Connect your backup drive -- use a usb-c adapter if needed.

OK, we're ready-to-go, so let's get goin':
8. Press the power on button for the first time.
9. The new Mac may ask for help "finding" the keyboard, just follow instructions.
10. Begin setup. At the appropriate moment, setup assistant will ask if you wish to migrate from another Mac or drive. YES, you want to do this.
11. "Aim" setup assistant at the external backup. Setup assistant will need a little time to "digest it all". BE PATIENT and give setup assistant the time it needs.
12. You will now see a list of things that can be migrated, such as applications, accounts, settings and data.
13. I suggest that you select ALL of them.
14. Let setup assistant "do its thing". It's going to TAKE A WHILE to move things over. Again, be patient. If you have a lot "of stuff", it will take a lot of time!
15. When done, you should see the login screen. Go ahead and login.
16. Once logged in, things should look pretty much as they looked on your old Mac.
17. You should check all your apps. Some may not run, and may require upgrading.
18. You can set aside the old backup, or ... "repurpose it" to become the backup for the new Mac. I'd keep the old one around for a week or so, at least.