Xianxia: Why am I here? - Chapter 54

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

Ten years ago, mana descended upon Earth in the form of Gates that opened into other worlds. These Gates contained Magical Beasts of unfathomable strength and power that preyed upon humans and sought the destruction of everything around them.But along with the Gates, humans gained the power of Gifts—super abilities that allowed them to fight back against the monsters and take back their world.Now, the Superhumans with Gifts are tasked with defending the people and ensuring that the Gates, which open all over the world, do not bring about the end of them all....Jason Marc was just your regular seventeen-year-old high school student whose father abandoned him ten years ago. He worked two part-time jobs while also helping his mom with her diner to aid with the finances, but he could have never guessed that his entire world would change on the eve of his eighteenth birthday.Now, with more power than any one man should possess and an army at his beck and call, Jason works toward protecting those close to him while finding out the truth behind the emergence of the Gates—and preventing the end of the world.

When she woke up, she had transmigrated into An Jiuyue, a woman living with two young children on a mountain after her husband abandoned her. She was pushed to the ground, and now, there was a bloody wound on her head.

With only a handful of rice left in the rice bag, she had relied on digging wild vegetables to satisfy their hunger every day. Her children were so often starved that they were all skin and bones. On top of that, a wicked woman threatened her to sell her son! If she refused, the woman would snatch him away forcefully.

But An Jiuyue took a deep breath, revealed her sharp claws, beat the woman up, and threw her out of the house. She could show the woman she was not to be messed with!

They were out of rice and vegetables now, but she was not afraid. Acquiring food using her spatial abilities was as easy as curling her fingers!

Moreover, her spatial abilities were unlimited, and her medical skills did not deteriorate. She could no doubt earn money and raise her children well!

As for her ex-husband…

The prince, who had returned from the battlefield, smiled maliciously. “My beloved concubine, please calm down. I brought back a mountain of gold from the battlefield as a gift for you and our children.”

I met the male lead in prison.