EM is Emergency declaration.

DR is Disaster declaration.

I like this resource:

https://www.fema.gov/disaster/declarations?field_dv2_declaration_date_value%5Bmin%5D=2024&field_dv2_...

It includes start and end dates, declaration level and date, and click on the disaster, it helps see details. That's why I also go to the declaration, in case it is only specific locales:

https://www.fema.gov/press-release/20241012/president-joseph-r-biden-jr-approves-major-disaster-decl...

It's coming up with a different number:

https://www.fema.gov/disaster/4834