Would like to know if a person married in civil rites to a non-Catholic 40 years ago then separated after five years of marriage and with 3 children needs an absolution from the Pope even if the person after separating confessed her sin and received absolution from a priest?
It may be that you are confusing “absolution” with “annulment” but in either instance the Pope would not normally enter the picture. Given that the person who married a non-Catholic is a Catholic, the civil marriage ceremony would have no standing in the Church. A simple declaration of nullity would be all that is required should that person want to marry in the Church. The amount of time that has passed since the attempted marriage and separation, even the instance and number of children, would be inconsequential to the ecclesiastical grounds against it being licit. Church law requires that Catholics have their marriages witnessed by a deacon or priest unless the appropriate dispensations have been granted. The absolution of a priest after a divorce or separation is a separate matter; however, if a Catholic should cohabitate with a civil law spouse, absolution could not be given.
If the person who married a non-Catholic was also a non-Catholic at the time of the civil ceremony, then the Church would consider that marriage as lawful and binding. If there was a divorce and either party wanted to marry in the Catholic Church, a formal annulment case would have to be entered and adjudicated by a Church Tribunal to determine the true validity of the prior bond. If the first marriage is shown to be binding and genuine, no second marriage could be permitted until the death of one of the spouses.