This is the 529th most frequent Czech word.
našich
"Našich" means "our" (genitive or accusative plural form).
'našich' is used as a possessive pronoun in the genitive plural form, modifying 'míst' (places), which is neuter plural in genitive.
Navštívili jsme jedno z našich oblíbených míst.
We visited one of our favorite places.
'našich' is the genitive plural possessive pronoun modifying 'školních let' (school years, plural in genitive case).
Vzpomínám si na dobré časy s našich školních let.
I remember the good times from our school years.
'našich' functions as the possessive pronoun in the locative plural form, modifying 'dokumentech' (documents), which is masculine inanimate plural in locative.