If you used the Desktop program then don't you still have it installed? Yes you need the state program installed to open a .tax2018 file. You can try to download it again, it might let you. You first need to start a fake return to be able to download the state program (go to File-New Tax Return). Then go to FILE -Open and find your return.
You didn't save it as a pdf file? If you only have the .tax2018 file and just need to print it out, you could try the TaxPrinter service to convert a .tax file to pdf at
http://www.taxprinter.com
They might be expensive and it is probably not safe to email tax returns back and forth. They are not related to Turbo Tax.
