How do I check if a malware download was successful on my computer?

Did you call this friend and ask if they sent you the photos? If they did, then you can be certain it's not a scam or any type of malware.

If this friend says they did not send you any photos, then stopping the download is all you needed to do.

Download-based malware for iPad is very rare.

Phishing messages and spoofed messages and related scams and the rest are far more common. Endemic, even.

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Enable two-factor authentication on your Apple Account, and use unique passwords everywhere, as well. It’s phishing and scams and re-used passwords and similar vulnerabilities — and not malware — that cause most of the problems.

Rather less likely to be necessary here or in general, but if you want higher difficulties for malware, enable Lockdown:

About Lockdown Mode - Apple Support

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