External SSD after Trojan infection. Safe to keep using after reinstall + clean scans?

About 9–11 months ago I infected my laptop with a Trojan after downloading what was supposed to be Cheat Engine from a sketchy GitHub repo (not the official source). I don’t know the exact malware family.

One extra detail that makes me unsure: before all of this happened, I had copied all files from my old laptop (which hadn’t been used for maybe 10 years) onto my external SSD.

Later, when I scanned the external SSD with Kaspersky, it detected several Trojans inside files that were around 10–15 years old. I deleted/quarantined those detections.

After the infection incident, I:

Reinstalled Windows using Media Creation Tool

Created the installation media from another clean device

Replaced the internal SSD

My external SSD was NOT connected during the reinstall

One thing I never did was format the external SSD.

Since then:

I’ve continued using the same external SSD normally for 9–11 months

No unusual behavior, missing files, popups, or performance issues

Recent Kaspersky scans show 0 threats

My questions:

Is it reasonable to assume the external SSD is safe now?

Could those old detected files have just been inactive infected files sitting in storage for years rather than an active infection?

Is it realistic for a Trojan to remain on an external SSD for almost a year with no detections or symptoms?

Would you still format the external SSD, or keep using it?

I’m mostly asking for peace of mind because everything has been behaving normally, but finding old Trojans from archived files made me second guess whether the SSD is actually clean.