Paking
It’ll give you a notification once it is done cooking, or the notification of “Cooking…” is gone. Now go to the Unreal Engine’s folder and follow this path starting from this screenshot.

Saved > Cooked > WindowsNoEditor > PAYDAY3 > Content > WwiseAudio
If you used Sound SFX or Music Containers, you want to copy Events and Media folders into that Wwise folder in your mod folder
Example:
Half-Life 2 Footsteps > PAYDAY3 > Content > WwiseAudio > Events
Half-Life 2 Footsteps > PAYDAY3 > Content > WwiseAudio > Media
If you used Sound Voice, you want to copy Events and Localized folders into that Wwise folder in your mod folder
Example:
Half-Life 2 VO > PAYDAY3 > Content > WwiseAudio > Events
Half-Life 2 VO > PAYDAY3 > Content > WwiseAudio > Localized
Now time to pack! Go back to the start of your mod folder

Click on the folder itself, right-click, and click on the option of “Pack with Repak”

Give it some time, and there should be a new file called your [modname].pak
Now you can put this .pak file into your ~mods folder in Papaya 3 and test if you like your mod

PAYDAY3 > Content > Paks > ~mods