The problem you face is expungement
is limited by state law
WI has an expungement process available for crimes committed when the accused was under the age of 18 at the time. If this applies to your circumstances, then yes...you can have the offense expunged. But if the conviction was under the age of 18 unless you were tried as an adult, it would not be a criminal conviction...so I assumed that did not apply to you.
THe other way is based on this provision of WI law
(a) Subject to par. (b) and except as provided in par. (c), when a person is under the age of 25 at the time of the commission of an offense for which the person has been found guilty in a court
for violation of a law for which the maximum period of imprisonment is 6 years or less, the court may order at the time of sentencing that the record be expunged upon successful completion of the sentence
if the court determines the person will benefit and society will not be harmed by this disposition. This subsection does not apply to information maintained by the department of transportation regarding a conviction that is required to be included in a record kept under s. 343.23 (2) (a).
So this is a rule that is a form of "deferred adjudication"
But it must be ordered at the time of the sentencing.
If that happend, then you would be able to apply to have the record expunged. But again, this is something that must happen at the time of sentencing. It is typically offered as part of the plea negotiations
If that did not happen in your case, the law would not apply.
Sorry to have to bear bad news.