How to use regex in cmd findstr? (Regex not working)

Question

I just see some regex could not work in windows cmd because it doesn't support all regex commands. I've found a regex for my problem.

So now I need to use findstr with this regex: (?si)(?:^(?<!.)|\R{2}|^Account:(?-s:.*)\R)\K(?:(?!\R{2}).)*?(?-s:\bfifa\b.*\b20\b).*?(?=\R{2}|\z) , but windows command line can't find this, and actually skips.

1. How can I use above regex, to find all matches from a txt file and output them to another txt file in a batch file?

This is how I used to do it with other simple regex, but not working now:

type %LogFILE% | findstr /i /r /c:"(?si)(?:^(?<!.)|\R{2}|^Account:(?-s:.*)\R)\K(?:(?!\R{2}).)*?(?-s:\bfifa\b.*\b20\b).*?(?=\R{2}|\z)" > %LogNEW%

2. Can we use powershell commands in cmd? I tried to do but it closes my batch command (I don't know is this correct syntax or no):

powershell -command "& {Get-ChildItem -Path .\LogFILE.txt -r | Select-String "(?si)(?:^(?<!.)|\R{2}|^Account:(?-s:.*)\R)\K(?:(?!\R{2}).)*?(?-s:\bfifa\b.*\b20\b).*?(?=\R{2}|\z)" > LogNEW.txt}"

EDITED: I want to select hits including fifa (as string not a single word) from a txt file, and output them to another txt file (separate solutions for 1 and 2 pattern):

Pattern 1 Solved: powershell -command "& {Get-ChildItem .\LogFILE.txt -r | Get-Content -Raw | Foreach-Object { $_ -Split '(\r?\n)(?=(\r?\n)+)' } | Select-String 'fifa'} | Out-File -encoding Default LogNEW.txt"

1:

Region: AR
OnlineID: Atl_Tuc
---Start---
FIFA 18 Legacy Edition
---END---

Region: FR
OnlineID: jubtrrzz
---Start---
FIFA 19
Undertale
Pro Evolution Soccer™ 2018
---END---

Region: US
OnlineID: Cu128yi
---Start---
KINGDOM HEARTS HD 1.5 +2.5 ReMIX
---END---

Region: RO
OnlineID: Se116
---Start---
Real Farm
EA SPORTS™ FIFA 20
LittleBigPlanet™ 3
---END---

Region: US
OnlineID: CAJ5Y
---Start---
Madden NFL 18: G.O.A.T. Super Bowl Edition
---END---

Pattern 2 Solved: powershell -command "& {Get-ChildItem .\LogFILE.txt -r | Get-Content -Raw | Foreach-Object { $_ -Split '(?<=---END---\s*\n)\s*\n' } | Select-String 'fifa'} | Out-File -encoding Default LogNEW.txt"

2:

Language: pt-BR (Actually I need [Language:.*])

Region: AR
OnlineID: Atl_Tuc
---Start---
FIFA 18 Legacy Edition
---END---

Language: en-US

Region: FR
OnlineID: jubtrrzz
---Start---
FIFA 19
Undertale
Pro Evolution Soccer™ 2018
---END---

Language: en-GB

Region: US
OnlineID: Cu128yi
---Start---
KINGDOM HEARTS HD 1.5 +2.5 ReMIX
---END---

Language: pt-BR

Region: RO
OnlineID: Se116
---Start---
Real Farm
EA SPORTS™ FIFA 20
LittleBigPlanet™ 3
---END---

Language: es-MX

Region: US
OnlineID: CAJ5Y
---Start---
Madden NFL 18: G.O.A.T. Super Bowl Edition
---END---

Answer 1

As per comment, this sounds like an XY Problem; You're so eager to resolve this your own way (trying to use a single regular expression in the old-fasion CMD with a limited FindStr command) that you probably lost the broader picture along with any other attempted solution.

For example:

In PowerShell

Get-ChildItem .\LogFILE.txt -r |
    Get-Content -Raw | Foreach-Object {
        $_ -Split '(?<=---END---\s*\n)\s*\n' # or: '(?<=Language:[\S\s]*\n)\s*\n'
    } | Select-String 'fifa'

Putting this in a CMD command:

powershell -command "& {Get-ChildItem .\LogFILE.txt -r | Get-Content -Raw | Foreach-Object { $_ -Split '(?<=---END---\s*\n)\s*\n' } | Select-String 'fifa'} > LogNEW.txt"