There are many ways to say "law firm" in Spanish. In some countries, the terms bufete jurídico or bufete de abogados are used, but never in Argentina or Uruguay, where law firms are called estudios jurídicos.
In Mexico and Spain, law firms are often called despachos de abogados.
In the Dominican Republic, you sometimes see the term gabinete de abogados (which is a calque of the French term for "law firm"--cabinet d'avocats).
Surprisingly enough, in Venezuela, the term escritorio jurídico is often used, although in standard Spanish an escritorio is a desk, not an office (but note that escritório is indeed the Portuguese word for office).
In some countries, you may even see firma de abogados.