Esto forum por cuestiónes en inglese. Puedo leer portoguesa un poco, ma non escribir en portuguesa. Mi repuesta es in inglese.
This is an English language forum. I can read Portuguese to some extent, but not write in Portuguese. (The above is in broken Spanish.)
For testing you can download and install Evaluation Edition. The trial is good for 180 days. But if you would be content with the outcome and actually migrate to SQL Server, you would have to buy a license. There is no free edition that is licensed for databases of 1TB.
Bear in mind that migrating from an RDBMS is a major work, unless queries strictly follow basic ANSI standard. And performance is more depending on how queries are written with regards to the product you are using and to indexing. It is likely to be a lot less cheaper investment to perform tuning of your current installation than to migrate. To wit, it is perfectly possible to have things to run slow with MS SQL Server as well, if you don't do it right.