LACIE PORCHE BACK UP DRIVE WITH A FIREWIRE 400 CONNECTION TO MY 2014 IMAC USB CONNECTIONS. WHAT DO I DO?

Sadly there is no USB port on that LaCie drive.

If you want to connect that LaCie to your 2014 iMac you will need two things.

1) an Apple ThunderBolt to FireWire 800 adapter.

Apple Thunderbolt to FireWire Adapter - Business - Apple

2) a FireWire 800 to FireWire 400 cable.

https://www.amazon.com/CY-Firewire-9-pin-FireWire-Capture/dp/B0BZ7Q1XKQ/ref=sr_1_5?

At this point I second the options offered by Kurt Lang, instead of spending money on an adapter and cable.

What model is the LaCie Porche external drive..?

Most of those older drives had both FireWire and USB ports.

If that LaCie model has both, then it is best to just use a USB cable in the USB port.

Also, please turn off the CAP lock key on your keyboard.

There is no possible way to plug a Firewire drive into a USB port. You will either have to:

1. Transfer the data off to another Mac that will allow you move it onto a newer external drive with a USB connector.
2. Take the drive out of the Firewire external housing and put it into one with USB ports.
3. If you have an older Mac the Firewire drive can connect to, you can put it into Target Disk Mode and connect the two Macs together. I believe that will allow you to see the Firewire drive from the older Mac.

You can use the instructions here to hook up a firewire drive to a new Mac with Thunderbolt. It is for DV cameras, but the FW hookup applies to Hard drives, too.

Getting DV (Digital Video) onto current M… - Apple Community

If it is the one in the following image,

then you need to find the original USB cable or buy a USB mini-B to USB-A cable.

Late to the party with this, but if you are moderately technically adept, you can open the drive, take out the hard drive and use a USB to IDE adapter to get at the data.

You can search your favorite shopping site for "USB to IDE adapters" but they look like this:

So there’s no model number and serial number sticker somewhere on this, maybe even on the bottom?