Learn Swedish: Jag vill köpa en sådan kappa.

The word sådan has to match the noun it describes, which is kappa (coat). Because kappa is an en-word (singular), we use the en-form sådan. If you were talking about an ett-word like hus (house), you would use sådant, and for plural words, you would use sådana.

Why is the word order en sådan kappa instead of sådan en kappa?

In English, we say "such a coat" (such + article). But in Swedish, sådan behaves like a normal adjective, so it goes right between the article and the noun. You are literally saying "a such coat" (en sådan kappa). This is a very common trap for English speakers, so it is good to memorize!

Could this sentence also mean "I want to buy a coat like that"?

Yes, absolutely! While "such a coat" is the literal translation, English speakers more often say "a coat like that" or "that kind of coat". En sådan kappa covers all of these meanings in Swedish.

Why is there no att (to) before köpa?