I'd like to know if exists any tool able to translate ontologies to OWL 2 DL. What I need is a converter able to take in input something like OWL, RDF, JSON, Manchester syntax etc etc... and convert it to OWL 2 DL format.
OWL 2 DL is not a format, as Stanislav mentioned. There are a number of defined formats to encode OWL 2 DL, many of which are only slightly different from the ones you mention - e.g., both OWL 1 and OWL 2 define a RDF serialization.
The DL bit refers to profile rules - an OWL 2 DL ontology needs all its classes and properties IRIs defined, for example (as opposed to OWL 2 Full or plain RDF).
OWL API can parse ontologies in a variety of formats, and, if the ontology is within the OWL 2 constraints, it can validate its profile. This will tell you whether an ontology conforms to the OWL 2 profile, and if not will give hints on what needs to change. See the OWL API wiki for examples on how to parse and save ontologies with it. https://github.com/owlcs/owlapi/wiki