'AmnLemKo' is the Lawbringer's runeword, requiring a sword, hammer, or scepter as a base, with swords being the most popular type. So, to make a Lawbringer sword, you need to put an Amn rune, a Lem rune, and a Ko rune into a 3-socket sword. But you must put them in the specified order and cannot be changed or adjusted. Also, you cannot put Diablo 2 Resurrected Items that runeword in a sword with more than three sockets.

You can get a 3-socket sword in the late game on Normal difficulty or higher, and you can also search for it in the Secret Cow Level. But when looking for a socketed weapon, you can't equip an item that increases the chance of a magic item, as it will make your chances of finding a socketed item lower. Except for the Short Sword, Scimitar, Sabre, and Falchion which Buy Diablo 2 Resurrected Items do not have three sockets, most other swords have three sockets, and the Crystal Sword is the most popular one.

The easiest of these to find is the Amn rune, which you can get in the Hellforge on Normal difficulty and drops randomly in Act IV on Normal difficulty. While the Ko rune only starts to drop in Act II on Nightmare difficulty, you can also get it from the Hellforge in Nightmare or Hell, or The Countess in Hell. The Lem rune will randomly drop starting from Act III on Nightmare difficulty, and you can also find it in the Hellforge on Nightmare or Hell difficulty, and The Countess on Hell difficulty.

Slain Monster Rest is the most prominent place for the Lawbringer in the Peace modifier. It can prevent some monsters from gaining the power of their fallen allies, and this ability is very effective against Nihlathak in Act V.

Of course if you don't want to go through such a hassle to get it, you can also buy it directly in MMOWTS, they will sell various Diablo 2 Resurrected Items including Lawbringer sword, any Diablo 2 Resurrected Items you need can be bought there arrive.