From Abyssal Invasion to Bursting Stars with a Single Sword - Chapter 100 - 93: Huan Yu Security Company, Forming a Team

To correct the mistakes of his past, a young man is forced to narrow the space between science and witchcraft, as he ventures on a quest to save his world from complete destruction.

The youngest A-rank adventurer, child prodigy Kaizer, finds three babies who were the only survivor of a destroyed village. Then he decided to give up his job as an adventurer and raise them. Over time, the girls grow brightly and show exceptional talents in fencing, magic and management. However, these girls also seem to love their father, Kaiser!

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.

Ever since He Mulan, a 28 year old forensic investigator, transmigrated into the post-army civilian Hua Mulan’s body, she’s been under a lot of pressure. Unlike the folktale ending, there are no flowers or applause to be found here. After leaving the army and returning to her hometown, word by the countryside has painted the now 32 year old Hua Mulan as a homicidal maniac, an old hag, and a freak of nature, among other nasty things. Between piecing together Hua Mulan’s scattered memories, grappling with her fellow villagers’ prejudice against her, and fending off Mrs Hua’s attempts to match make her, He Mulan has her hands full. All He Mulan wants to do is protect Hua Mulan’s body till her soul comes back, but fate has other plans…

- Description from Novelupdates