Hi Miran.
Unfortunately you may have to either order the grains specially or resign to brewing with the ingredients that you have available.
An imperial milk stout would need chocolate malt, a biscuit type base malt like Maris Otter, and other specially crystal malts.
You will also need lactose. I would suggest brewing less complicated beers, and getting a foundation for brewing. Not being negative or rude, but it seems you don't fully have a grasp on Malts and their relationship to each other and the final outcome of a beer.
Mashing is a very complex process and to get great, repeatable beer that's actually enjoyable takes considerable knowledge unless you are following tested recipes.
So, unless you have a thorough understanding between malts, diastatic power, kilning, crystal vs roast vs base, residual sugars, PPG, colour, what each malt does to the PH of the mash, each malt profile and what each malt contributes to the beer among other things, simply throwing what you consider to be "similar" ingredients in will not produce good beer.
Perhaps focus on what you have available, and look at brewing simpler beers. An imperial milk stout may require a reiterated mash to get the right OG, you need to consider BU:GU ratios and other things besides the mash ingredients.
Get yourself some good quality base malt, and focus on producing some Single Malt and Single Hop (SMaSH) beers to get a foundation of what you're doing.
Additionally you need to properly understand your system and its efficiency, because the higher you go in malt bill generally the less efficient you become. After one brew you won't have any idea about what your system efficiencies are and you are likely to miss your target numbers by a large margin.
Unless you then boost with DME your GU:BU ratios will be off among other things. So even IF you had a recipe, and the ingredients, you won't know if you will hit the numbers.
