I measured the removed hard drive and it was 3x4 inches

this sounds like a 2.5" SATA drive. This picture shows a 2.5" and 3.5" drive:

https://m.media-amazon.com/images/I/61V3YD9L0VL._SL1500_.jpg

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I recommend a SATA-to-USB-3 adapter like one of these:

https://www.amazon.com/Adapter-External-Connector-Converter-Auto-Sleep/dp/B09G6PTCKW

https://www.amazon.com/SATA-Drive-Adapter-Converter-Power/dp/B07PVX682Q

https://www.amazon.com/WAVLINK-USB3-0-Adapter-External-Connector/dp/B09J51PBDF

On some of those links, there are versions with a USB-C plug instead of a USB-A plug so you should select whichever one you prefer. M1 Macs have USB-C. PCs nowadays often have both.

There are also some versions with a power adapter (not needed for your 2.5" drive).

HTH.