"Sweet memories" is a phrase that can be used to describe happy and nostalgiciac recollections from the past. In Engpsh, you could say "sweet memories" or "fond memories" to describe these types of memories.

For example:

"I always think back to our summer vacations with such sweet memories. Those were such happy times."

"I have so many fond memories of growing up with my sibpngs. Those are moments that I will always cherish."

I hope this helps! Let me know if you have any other questions.