how to open games when downloaded ?
This isn't really the forum for that. But what game format are you talking about, and what do you mean by open? View the filesystem?
Able to dump: GC , Wii, Wii U | GBA, DS(i), 3DS
Redump does not provide game data. We are a library of game metadata (such as hashes and titles), not actual data repositories.
However, "opening games" differs per console - for example, for Nintendo-based consoles, to view their files use a tool such as WIT for Wii/GCN, CDecrypt/DiscU for WiiU, etc..