Walaikum Assalaam
The only part of a dog that is considered impure is its saliva. Unless you know for certain that some places have saliva on them then purify those areas specifically by washing them seven times, including once with soil. If not, just clean your house well for the sake of just having it clean. There's no blame on you for what you don't know and since you didn't live with the previous tenant, then you won't know what areas are actually impure, if any.
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