Hi there
I just converted on Saturday and now I feel the need to make a good confession. The last time I learned how to make a good confession was in grade 3 religion class and I am 22 years old so I don’t really remember the paper at all. If anyone has any resources or advice for me I would greatly appreciate it
God Bless
If you haven’t confessed in years and years.
You might be more comfortable organising a private appointment with a priest outside of usual confession times, or by visiting a monastery and asking for a priest there to hear your confession,
(rather than waiting in a queue, if you have a lot to say)
A helpful guide is to Google the Catholic catechism and read each of the chapters for the 10 commandments, (breaking of the commandments is usually grave matter),
A few rules

At confession every mortal sin not confessed since your last confession, must be confessed (that you remember),
Hiding and not telling a mortal sin deliberately (is the sin of sacrilege meaning nothing in the confession will be forgiven and adds another mortal sin to the soul)
Venal sins do not have to be confessed but can be mentioned if you are unsure whether they are venial or not
Mortal sin is grave matter committed deliberately with full freedom and full knowledge. Grave matter examples: not doing the Ash Wednesday or Good Friday fast of three meals and no meat. Not doing some form of penance or abstaining from meat on all Fridays of the year (in honour of Jesus Passion). Not confessing once a year during the Easter season. Receiving communion in a state of mortal sin is a mortal sin. Hiding mortal sins in confession (not saying them deliberately). Not doing some form of penance in Lent. Deliberately not going to Mass on Sundays and holy days.
Other examples of grave matter: masturbation, pornography, fornication, adultery, murder, causing serious harm to someone by word or action, using Gods Name of Holy Names as swear words is grave matter, atheism is grave matter (against the first commandment),
Leading others to sin gravely in any of the above (by encouraging them in words or by your example is grave matter also)
Deliberately not doing good can be grave matter if it causes serious suffering to someone else such as:
Didn’t feed your pet bird and the bird starves to death (so sometimes not doing good can be grave matter also, if the neglect caused serious harm to someone),
The priest will guide you what to say and ask questions to help you identify your sins if you ask.
Just some starting points!