I found money on the street. I want to ask what I must do with this money.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Anyone who finds some waif which is of some value like gold, silver, a device, etc., he should declare publicly that he has found some thing lost and wait for the owner who is the one who describes accurately the object and return it and to him. But if the waif is insignificant, or its owner is not keen on getting it back, the finder is not then required to declare having such object publicly and it is lawful for him to take it and benefit from it. Ibn Qudamah says: 'We do not know any disagreement among scholars regarding the lawfulness of taking insignificant waif and profiting from it. This is reported from Umar , Ali , Ibn Umar and Ayisha (Radiya Allahu Anhum). It is also reported from Ata'a , Jabir Ibn Zaid , Tawoos , al-Nakhai , Yahya Ibn Abi Katheer , Malik , al-Shafi'e , … etc.' .
The limits of an insignificant thing are conventional according to the most preponderant opinion.
It is also lawful to take what the Prophet (Sallallahu Alaihi wa Sallam) himself mentioned like the whip, the stick, the rope and anything that has a similar value. The evidence for this is the Hadith reported from Abu Dawood from Jabir that he said: "The Prophet (Sallallahu Alaihi wa Sallam) permitted us to take the stick, the whip and the rope and similar objects which the person picks up and gets profit from it" .
So, if the person finds a valuable waif, he has to declare this publicly in markets, in front of doors of mosques, in newspapers and anywhere people gather. If a year passes after he makes such announcements and the owner does not show up then the object becomes his own regardless of whether he is rich or poor. This is the opinion of al-Shafi and Ahmad Ibn Hambal unless its owner shows up, then he has to assure it for him.
Allah knows best.