If you made bets on new platform then you can easily see your last bets through API
https://api.primedice.com/graphql and get seed from it.
Just paste this code and run it:
query userid{user(name: "YOUR_USERNAME_GOES_HERE"){betList{iid}}}
Personally I have received such answer:
{
"data": {
"user": {
"betList": [
{
"iid": "23782704876"
}
]
}
}
}
What does all this mean?