First, you need the following:

1. Secret Style DLC purchased[slimerancher.fandom.com]

2. Viktor's Workshop unlocked[slimerancher.fandom.com]

Then,

Enter the Slimeulation.[slimerancher.fandom.com]

The Retro Pod is located at the south-western area of the Moss Blanket (where the Honey Gordo[slimerancher.fandom.com]usually would be). However, the map looks a bit different than normal while in the Slimeulation, so it can be hard to navigate.

For me, I eventually found it by wandering through all the Moss Blanket areas until it pointed me to an exit gate, where I was able to spot the pod next to the gate. Didn't take me too long. You'll eventually figure out the Slimeulation map differences after doing the minigame a handful of times.

Thx man