Biblically, the word 'flesh' represents man's predilection toward sin.
When Adam chose to disobey God’s command, he became sinful flesh. Through that immoral act, the entire world was corrupted. Animal life, plant life, and even the ground itself no longer resembled the paradise that was Eden. Originally, there was no such thing as 'death' ... now it permeated everything.
Since the entire human race descended from Adam, mankind inherited his fallen nature (and its consequences) ... Therefore, as sin came into the world through one man and death through sin, so death has spread to all men, because all have sinned. (Romans 5:12)
It became impossible for us to keep God's divine law ... Those who are in the flesh cannot please God. (Romans 8:8)
To understand what it meant for Jesus to come 'in the likeness of sinful flesh', we need to define the term 'likeness'.
It means resemblance to, not identical to (in substance or nature) ... And being found in appearance as a man, He humbled Himself and became obedient to the point of death, even the death of the cross. (Philippians 2:6-8)
Jesus did not have an earthly father. Therefore, He did not have Adam's sin nature. The Lord took on human flesh by being born of a woman, yet retained His divinity.
As such, the Lamb of God was able to present Himself as the final perfect sacrifice, more than sufficient to pay for every sin committed by mankind ... He became the Mediator of a new covenant, so that those who are called may receive the eternal inheritance (since He died to set them free from the violations committed under the first covenant). (Hebrews 9:15)
To receive that full pardon, you must embrace Christ as Lord. Salvation is received by grace through faith in His finished work ... God made Him who had no sin to be sin for us, so that in Him we might become the righteousness of God. (2 Corinthians 5:21)
Your sinful flesh will be dealt a death blow. You can then proclaim with Paul ... I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me. (Galatians 2:20)
Trust Him and be free.