Base malts give the highest pH in deionized water (DI pH,) Pilsner usually around 5.9, US and British pale maybe 5.5-5.7; crystal malts are more acidic, and roast malts even more so, some with a DI pH below 5.0. Of course, in natural water supplies, or water you build from DI, this will be significantly different.
But it's not like you can just add a malt to raise pH anyway (though you might add some crystal or roast malt to lower it.) Your grain bill is a given, defining the beer you want to make. To manipulate the mash pH, you need to adjust the water chemistry, adjusting the mineral ions it contains. Minerals can be added, and if necessary removed by RO or by dilution or replacement with RO or distilled water and then adding desired minerals back in. Increased calcium can, to some extent, lower mash pH, with organic or mineral acid additions being more effective. Raising mash pH generally calls for an increase in alkalinity in the water, effected by adding either sodium bicarbonate aka baking soda (which can add way too much sodium) or calcium hydroxide aka pickling lime (though this is a balancing act, since while the hydroxyl group wants to raise mash pH by increasing total alkalinity, the calcium wants to lower it by reducing residual alkalinity.)
*I highly recommend reading the page BrewBama linked,* and, if you run Excel, try the Bru'n Water spreadsheet from that site as well to plan water treatment. An alternative to this spreadsheet is the advanced water chemistry calculator at Brewer's Friend.
To know your starting point, if you consistently use the same source, get a water report from your utility or a testing service like Ward Labs.
For a deeper dive into what you are actually trying to do and why, which might help you work all this out on your own, you can try the Water book by Palmer and Kaminski from the BA's Elements series. There are also some extremely dangerous rabbit holes on this and other forums.
Hope this helps.