As there is such concept in the Russian language as the category of gender (that can often be determined through word's ending), then the endings of each gender will be changed according to gender in the formation of plural form.
Forming the plural form of masculine nouns which often have zero ending in singular form (sometimes, -А [a], -Я [ya]) we add the ending -Ы [y], -И [i]. Pay attention that we exactly "add" the ending. We do not change the stem of words, if only it is not atypical ending like -Ь.
Журнал – журналы [zhurnal - zhurnaly] - magazine - magazines
Камень – камни [kamen' - kamni] - stone - stones
Стол – столы [stol - staly] - table - tables
There are some exceptions. For example, the word «дом» [dom] (house) has the ending -A in plural – «дома» [dama] (houses), and the word «стул» [stul] (chair) turns into «стулья» [stul'ya] (chairs).
The endings of feminine nouns are changed: the ending -А [a] turns into -И [i], -Ы [y], the ending - Я [ya] into -И [i].
Земля – земли [zimlya - zemli] - ground - grounds.
Кошка – кошки [koshka - koshki] - cat - cats.
Машина – машины [mashina - mashiny] - car - cars.
The endings of neuter nouns are also changed: the ending -О [o] changes to -А [a], the ending -Е [e] changes to -Я [ya].
Облако – облака [oblaka - ablaka] - cloud - clouds.
Зеркало – зеркала [zerkala - zerkala] - mirror - mirrors.
Pay your attention to the exceptions. This rule is not applied to the word «яблоко» [yablaka] (apple), the plural form in this case is «яблоки» [yablaki] (apples).
You can also find the articles on so-called "paired" gender on this website . It is about those words which we use only in the plural form as they don't have a singular form. These words have the endings like masculine and feminine nouns in plural form (sometimes, the ending -A that is typical for neuter gender, plural) and no singular form at all.
Деньги [den'gi]. Брюки [bryuki]. Чернила [chirnila]. - Money. Trousers. Ink