Each person experiences a breakup in their own way. Three months will be enough for someone to fully recover and successfully survive the stages of grief. Another will need a year, two, in some cases the trauma is experienced for more than a dozen years, and the person never starts a serious relationship.
You need to look at your own condition. If there is a sense of harmony, painful memories do not bother, there are no fears, then you can move on to a new relationship. It's not worth rushing. For a new relationship to bring joy, you must completely let go of the past.
In any case, there should be a period to be alone, to fully understand and experience what happened. If you immediately enter into a new relationship after a breakup, trying to forget the old ones, this can lead to disappointment. The psyche during this period has not yet adapted to new circumstances.
You should be guided by your own inner feelings. If an attempt to start a new relationship is associated with discomfort, then it is worth waiting for a while, sorting out yourself. You may not have gone through all the stages of grief.
You need to enter into a relationship when you feel ready to accept a new partner, and memories of the former no longer evoke strong emotions.