Unusual activity detected from Russia - Microsoft account

Hi all- sorry if this post doesn't make sense but I'm panicking a little. Got this email last night. On a old account I haven't used in about 2 years.

Microsoft account Security alert We think that someone else might have accessed the Microsoft account (email). When this happens, we require you to verify your identity with a security challenge and then change your password the next time you sign in. If someone else has access to your account, they have your password and might be trying to access your personal information or send junk email. If you haven't already recovered your account, we can help you do it now. Recover account

Logged in and this came up as recent activity Device/platform Windows Browser/app Microsoft Edge Session activity Unusual activity detected Approximate location Russia.

Is this an indication of someone successfully logging into my account or of someone attempting to?

Although it's old - I do have very sensitive info on there, so am very worried.

I have done all the security recommendations.

Thanks for any advice in advance.