'At' is denoted by the locative case.

location, local, locative, locale

The distinguished Spanish surname Casarez is of toponymic and locative origin. It is of toponymic origin when it is derived from the name of the place of residence of the original bearer; it is of locative origin when it is derived from a natural or man-made feature of the dwelling place of the initial bearer. ( answer from google)

Quintus ambulat ad tabernam in Roma. That one's close - but needs a couple of changes. Quintus ad tabernam Romae ambulavit. Ambulavit = walked (Ambulat = walks) This sentence is one of the few places where a rarely used Latin case comes in - the locative case. The word for Rome is put in locative (Romae) to indicate place where.

Nyumba, both sing, and pl. In the locative form (at home, to home, from home) it is nyumbani, which the ni at the end conveying the prepositional meaning without an additional word.