How update Laravel to 6? - laravel

Question

I am trying to upgrade laravel to version 6 to php 7.4. How can I change the composer (its content is below) so that it pulls the plugins of compatible versions necessary for the project?
Compatibility errors occur when changing only laravel version
how do I understand which versions of plugins to write in composer so that it builds projects correctly? I have a lot of problems with him when changing versions ...
{
"name": "Codecast's Single Page Application Starter Kit",
"description": "This is the web service to support the kit.",
"keywords": ["framework", "laravel"],
"license": "MIT",
"type": "project",
"minimum-stability": "dev",
"prefer-stable": true,
"require": {
"php": ">=5.6.4",
"laravel/framework": "5.3.*",
"barryvdh/laravel-cors": "0.8.*",
"tymon/jwt-auth": "~1.0",
"predis/predis": "~1.1",
"league/fractal": "0.14.*",
"jenssegers/agent": "^2.6"
},
"require-dev": {
"fzaninotto/faker": "~1.4",
"mockery/mockery": "0.9.*",
"phpunit/phpunit": "~5.0",
"symfony/css-selector": "3.1.*",
"symfony/dom-crawler": "3.1.*",
"squizlabs/php_codesniffer": "~2.3",
"scriptixru/sypexgeo": "0.2.*#dev"
},
"autoload": {
"classmap": [
"database"
],
"psr-4": {
"App\\": "app/"
}
},
"autoload-dev": {
"classmap": [
"tests/Support/",
"tests/TestCase.php",
"tests/ApiTestCase.php"
]
},
"scripts": {
"post-root-package-install": [
"php -r \"file_exists('.env') || copy('.env.example', '.env');\""
],
"post-create-project-cmd": [
"php artisan key:generate"
],
"post-install-cmd": [
"Illuminate\\Foundation\\ComposerScripts::postInstall",
"php artisan optimize"
],
"post-update-cmd": [
"Illuminate\\Foundation\\ComposerScripts::postUpdate",
"php artisan optimize"
],
"test": "phpunit --colors=always",
"check-style": "phpcs -p --standard=PSR2 --runtime-set ignore_errors_on_exit 1 --runtime-set ignore_warnings_on_exit 1 ./app ./config ./routes",
"fix-style": "phpcbf -p --standard=PSR2 --runtime-set ignore_errors_on_exit 1 --runtime-set ignore_warnings_on_exit 1 ./app ./config ./routes"
},
"config": {
"preferred-install": "dist"
}
}