So, how hard is it to find the right order of 12 words? There are ~480 million permutations of those 12 words. Luckily, because of the BIP39 standard we have some advantage, the 12th word is a checksum. So only 1 in 12 of those permutations constitutes a valid mnemonic. We are down to 14 paragraphs with ~50 million valid mnemonics from each.