Why was the plural form used in the following from the KJV? ( I have used this translation here because
so many readers will not consider any other.)
Hebrews 1:2 King James Version
Hebrews 11:3 King James Version
Even though worlds or even world is not mentioned in either the Greek Interlinear or the Peshitta.
We can get an inkling of thought from
bibleask.org
so many readers will not consider any other.)
Hebrews 1:2 King James Version
2 Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;
Hebrews 11:3 King James Version
3 Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.
Even though worlds or even world is not mentioned in either the Greek Interlinear or the Peshitta.
We can get an inkling of thought from

Did God create other worlds? - BibleAsk
The question of whether God created other worlds is one that has intrigued theologians, scholars, and believers for centuries ...

What say you???God and the Other Worlds
The Bible indicates that God chose to also create other worlds: “God, who at various times and in various ways spoke in time past to the fathers by the prophets, has in these last days spoken to us by His Son, whom He has appointed heir of all things, through whom also He made the worlds” (Hebrews 1:2; 11:3).
All these other worlds are un-fallen (Revelation 5:13). Jesus eluded to that in His parable: “What man of you, having an hundred sheep, if he loses one of them, doth not leave the ninety and nine in the wilderness, and go after that which is lost, until he find it?” (Luke 15:4). Jesus left these sinless worlds to come to this one lost world to save the creatures that are made in His image (Genesis 1:27).
In the book of Job, the Bible speaks of a heavenly council meeting in which the “sons of God” gathered before the Lord—and Satan showed up to represent our planet (Job 1:6, 7). Job 38:6, 7 also seems to indicate that these “sons of God” existed before our world was made.
Our world is a stage on which the conflict between evil and good, truth and error, is going on before the inhabitants of the universe. “For we are made a spectacle unto the world, and to angels, and to men” (1 Corinthians 4:9).
However, these un-fallen worlds can not contact us because they are restricted from mingling with us. Our planet is infected with the deadly contagious disease of sin, and we are likely quarantined. The only ones that can help the patients in a quarantined hospital ward are the medical staff; in our case, God’s angels.
While the Bible supports the idea that there is life on other worlds, we should be careful to remember that the devil and his angels can easily create illusions to deceive us by posing as aliens or celestial beings from other worlds pretending to help humans. The Bible says, “For Satan himself transforms himself into an angel of light” (2 Corinthians 11:14) in order to deceive people with his lies. Devils can work incredibly convincing miracles (Revelation 13:13, 14).
We don’t know where these other creations live right now but the good news is that Jesus will come again soon to end the sin problem. After Christ’s second coming, the saved will be able to tour the universe freely and visit all of God’s other worlds.